Photosynthetic co-culture system of algae and human umbilical vein endothelial cells:The effect on alleviating hypoxia and hypoxia/reoxygenation injury

It is a developed photosynthetic co-culture system to alleviate the hypoxia and hypoxia/reoxygenation(H/R)-injured human umbilical vein endothelial cells(HUVECs).The algae,Chlorella vulgaris,were encapsulated to slow their growth while not affecting the photosynthetic oxygen-producing capacity by Layer-by-layer(LbL)using gelatin and sodium alginate as the positive and negative charges materials,respectively.Then,the photosynthetic co-culture system of HUVECs and self-oxygenating alginate hydrogel(Algae-gel)was constructed in which the optimal ratios between algae and HUVECs were 5:1 and 20:1 for a 2D or 3D co-cultured manner,respectively.It indicated that the 3D cocultured manner of HUVECs needed more O_(2) by the production of algae than it did in a 2D co-cultured manner.The co-cultured Algae-gel could alleviate hypoxia and the oxidative stress injury of hypoxia and hypoxia/reoxygenation(H/R)-treated HUVECs in the proliferation,intracellular ROS and cellular migratory ability.In addition,the Algaegel could downregulate the expression of hypoxia-inducible factors 1α(HIF-1α)and vascular endothelial growth factor(VEGF)of hypoxia and H/R-injured HUVECs due to the improvement of hypoxia and H/R injury.This photosynthetic co-culture system could offer a promising approach for repairing hypoxia and H/R-injured cells or tissue by providing safe and stable O_(2).

Bio‐inspired low wear and durable lubrication interfacial system based on thixotropic hydrogel for artificial joints

Inspired by the excellent wear resistance and lubrication of articular joints,a novel bionic interfacial system was proposed by combining thixotropic hydrogel with surface porous Ultrahigh Molecular Weight Polyethylene(UHMWPE).Thixotropic hydrogel,synthesised by gelatin,alginate sodium,tannic acid and weak crosslinking by Ca2þ(Gel‐TA‐Alg@Ca2þ),was used as a lubricant due to its shear‐thinning when loaded,then the re-covery viscosity to be benefitted for reserving in surface pores on UHMWPE when unloaded.Surface porous UHMWPE was fabricated by using hydroxyapatite particles as porogen to control its porosity,pore size,surface roughness and surface energy(PE‐HA).Gel‐TA‐Alg@Ca2þsignificantly reduced average coefficients of friction and wear factors compared to those under normal saline and calf serum solution lubricating after recipro-cating tribological testing.Notably,Gel‐TA‐Alg@Ca2þstill maintained thixotropy and was stored in surface pores of UHMWPE even after tribological testing for 7200 min.Thus,durable lubrication could be realised due to the synergistic effect of surface porous structure and thixotropy.Stribeck curves showed the characterisations of mixed,elasto-hydrodynamic and hydrodynamic,but without boundary lubrications for PE‐30HA under three lubricants.The present results might provide the potential application to construct the durable lubrication bionic articular joint interfacial system for artificial joints.

Fabrication and Characterization of Gecko-inspired Dry Adhesion, Superhydrophobicity and Wet Self-cleaning Surfaces

In this study, gecko-inspired polydimethylsiloxane （PDMS） microfiber surfaces were fabricated by combining Inductively Coupled Plasma （ICP） and micro-mold casting. The effect of roughness and surface energy of counterface on the adhesion of gecko-inspired microflber surfaces and its superhydrophobicity and wet self-cleaning were studied. The adhesion of gecko-inspired microfiber surfaces depended on the roughness of the eounterfaces due to the influences of contact area and interlocking mechanism. SEM images of interfaces between counterfaces with different roughness and gecko-inspired mi- crofiber surfaces revealed the matched and dis-matched contact directly. The gecko-inspired microfiber surface got the larger adhesive force from the higher surface energy counterface, which is consisted with Johnson-Kendall-Roberts （JKR） theory. The smaller dimension and lower duty ratio of microfibers on PDMS resulted in the increasing of Water Contact Angle （WCA） and the decreasing of Sliding Angle （SA） compared to those of smooth PDMS. Particularly, sample P-8-28-20 had the biggest WCA （155°） and SA （7°）, which displayed the superhydrophobicity and the best wet self-cleaning efficiency in all samples. The present studies showed that the roughness and surface energy of counterface both affected the adhesion of gecko-inspired microfiber surfaces. The smaller dimension and lower duty ratio of microfibers on PDMS endowed it with the superhydro- phobicity and the wet self-cleaning abilities.

Reconstruction of Surface Porous PEEK Decorated with Strontium-doped Calcium Phosphate Coatings for Enhancing Osteogenic Activity

The aim of this study was to reconstruct surface porous structure with hundreds of micrometers and then bio-mineralize Sr-doped Calcium Phosphate(Sr-doped CaP)on Polyetheretherketone(PEEK)profile to enhance its bioactivity.A surface porous structure was prepared on PEEK profile by embedding and acid-etching of SiO2 particles as porogen(SP-PEEK).Then the Sr-doped CaP was further decorated on the porous surface after sulfonation,introduction of Sr-doped CaP crystal seeds and bio-mineralization in 1.5 times simulated body fluid(BSSP-PEEK-CaP/Sr).It was feasible to reconstruct the surface porous structure with hundreds of micrometers on PEEK profile by the present method without damaging its mechanical properties.The Sr-doped CaP crystal seeds effectively promoted the bio-mineralization of bio-inertness PEEK.All as-prepared PEEK did not inhibit the proliferation of cells.ALP of bio-mineralized groups was significantly increased than that of the other groups.The BSSP-PEEK-CaP/Sr obviously affected the morphology and promoted the adhesion and spreading of cells.As a result,the cyto-biocompatibity and bioactivity of PEEK were improved after bio-mineralization.Sr-doped CaP on PEEK most likely was beneficial for cells,which was associated with the increasing of the hydrophilicity on PEEK.This study provided a candidate method to improve the osteogenesis of PEEK implants.

3D Printing of Well Dispersed Electrospun PLGA Fiber Toughened Calcium Phosphate Scaffolds for Osteoanagenesis

Although the toughening of Calcium phosphate(CaP)scaffold by the addition of fiber has been well recognized,integrated mechanical,structural and functional considerations have been neglected in the design and fabrication of CaP scaffold implant.The emerging 3D printing provides a promising technique to construct CaP scaffold with precise size and elaborate microstructure.However,the most challenge is to extrude smoothly the CaP paste containing fibers for frequently-used extrusion-based 3D printing.In this study,frozen section and chemical dispersant(Pluronic F127,F127)were employed jointly to prepare non-aggregated polylactic-co-glycolic acid(PLGA)fibers.The injectability of CaP pastes with well dispersed PLGA fibers was more than 90%when the content of PLGA fibers was no more than 3 wt%.Meanwhile rheological property of CAP pastes with well dispersed fibers showed shear thinning,which were both beneficial to extrude CaP paste with well dispersed fibers for 3D printing.Moreover,these CaP scaffolds showed ductile fracture behavior due to the pullout and bridging effect of PLGA fibers.The cell proliferation and alkaline phosphatase(ALP)activity indicated that 3D printed CAP scaffold containing PLGA fibers possesses excellent biocompatibility and facilitate osteogenic differentiation ability.Thus,it was feasible to print CaP pastes with well dispersed PLGA fibers to construct toughening CaP scaffolds with the higher shape fidelity and complex structures,which had significant clinical potentials in osteoanagenesis due to their higher toughness and excellent biocompatibility.

Osteoblast behaviors on titania nanotube and mesopore layers

Titania nanotubes and mesopores with different diameter sizes were prepared by electrochemical oxidation of titanium.The responses of osteoblastic cells isolated from Sprague–Dawley rats to the nanotube and mesopore layers were investigated in sequential events of cell adhesion,morphology,actin cytoskeleton,proliferation,differentiation,and mineralization.Nano-structural features,especially diameters of the nanotubes and mesopores,obviously influenced on cell behaviors in the sequential events.The cells showed better proliferation and differentiation abilities on the specimens with the nanotubes and mesopores than on flat titanium disk.Higher levers of calcium mineralization were observed on the nanotube and mesopore layers.The cells adhered much faster onto the nanotubes with about 170nm diameter and the mesopores with about 400nm diameter than onto flat titanium disk and 50nm nanotubes.There is an appropriate range of the tube/pore sizes,and in this present work,titania nantubes with 170nm diameter is the best for enhancing functions of osteoblasts.

3D-printed Mechanically Strong Calcium Phosphate Cement Scaffold with Metformin/Stem Cell-encapsulating Alginate Microbeads for Bone Tissue Engineering

The utilization of Calcium Phosphate Cement(CPC)is limited due to its low mechanical strength and difficulty to seed cells deep into the scaffold.The objectives of this study were to:(1)develop a 3D-printed CPC-dopamine-metformin scaffold encapsulating human periodontal ligament stem cells(hPDLSCs),(2)investigate the effect of dopamine on the performance of CPC,and(3)evaluate the effect of microbead degradation and metformin release on the osteogenic differentiation of the released hPDLSCs.The mechanical property of the CPC scaffolds was elevated by adding dopamine,and the CPC scaffold with 7 wt.%dopamine had the highest compressive strength(7.35 MPa).Four types of microbeads with different content of alginate(oxidized alginate),hPDLSCs,and 2%metformin were fabricated.Morphological and cell counting kit tests confirm that the hPDLSCs are protected by microbeads encapsulation during the CPC setting process.The alkaline phosphatase test indicates that the osteogenic differentiation of hPDLSCs was enhanced by the fast release of cells and metformin.The microbeads consisting of 2%oxidized alginate and 2%metformin were optimal for cell delivery due to favorable cell release and osteogenic differentiation.This CPC scaffold is promising used for bone regeneration in dental,craniofacial,and orthopedic applications.

Enhanced Adhesion of Mussel-inspired Adhesive through Manipulating Contents of Dopamine Methacrylamide and Molecular Weight of Polymer

The aim of this study is to investigate the effect of the contents of modified 3, 4-dihydroxyphenyl-L-alanine （DOPA）, named as do- pamine methacrylamide （DMA）, on the adhesion of mussel-inspired adhesives in air and water. A series of adhesives, p（DMA-co-MEA）, were synthesized by copolymerized DMA and methoxy ethylacrylate （MEA） with the content of DMA from 2 mol.% to 10 mol.%. Results of IH NMR show that the contents of DMA in all adhesives are near to the theory ratios of DMA in the staring reagents. Adhesives with more than 5 mol.% of DMA appear adhesion, while adhesives with 2 mol. % and 3 mol. % of DMA show almost no adhesion in air and water. Adhesive with 7 mol.% of DMA has the highest molecular weight and adhesion either in air or in water in all adhesives. Adhesion of adhesive is synergistically influenced by the content of DMA, molecular weight and elastic modulus of adhesive. It is because that higher content of DMA would provide more DOPA, which leads to the coordination bond between DOPA and metal ions. It is feasible to develop the mussel-inspired adhesive through incorporating DMA into polymers, which will have potential application in the clinic.